Physiologically activated mammary fibroblasts promote postpartum mammary cancer
Qiuchen Guo, Jessica Minnier, Julja Burchard, Kami Chiotti, Paul Spellman, Pepper Schedin
Qiuchen Guo, Jessica Minnier, Julja Burchard, Kami Chiotti, Paul Spellman, Pepper Schedin
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Research Article Oncology

Physiologically activated mammary fibroblasts promote postpartum mammary cancer

Abstract

Women diagnosed with breast cancer within 5 years of childbirth have poorer prognosis than nulliparous or pregnant women. Weaning-induced breast involution is implicated, as the collagen-rich, immunosuppressive microenvironment of the involuting mammary gland is tumor promotional in mice. To investigate the role of mammary fibroblasts, isolated mammary PDGFRα+ cells from nulliparous and postweaning mice were assessed for activation phenotype and protumorigenic function. Fibroblast activation during involution was evident by increased expression of fibrillar collagens, lysyl oxidase, Tgfb1, and Cxcl12 genes. The ability of mammary tumors to grow in an isogenic, orthotopic transplant model was increased when tumor cells were coinjected with involution-derived compared with nulliparous-derived mammary fibroblasts. Mammary tumors in the involution-fibroblast group had increased Ly6C+ monocytes at the tumor border, and decreased CD8+ T cell infiltration and tumor cell death. Ibuprofen treatment suppressed involution-fibroblast activation and tumor promotional capacity, concurrent with decreases in tumor Ly6C+ monocytes, and increases in intratumoral CD8+ T cell infiltration, granzyme levels, and tumor cell death. In total, our data identify a COX/prostaglandin E2 (PGE2)–dependent activated mammary fibroblast within the involuting mammary gland that displays protumorigenic, immunosuppressive activity, identifying fibroblasts as potential targets for the prevention and treatment of postpartum breast cancer.

Authors

Qiuchen Guo, Jessica Minnier, Julja Burchard, Kami Chiotti, Paul Spellman, Pepper Schedin

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Figure 3

In vitro mammary fibroblast activation by TGF-β1 is directly inhibited by ibuprofen.

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In vitro mammary fibroblast activation by TGF-β1 is directly inhibited b...
Treatment conditions are: 0.5 TGF-β1 = 0.5 ng/ml TGF-β1, 5 TGF-β1 = 5 ng/ml TGF-β1, Low IBU =10 μg/ml ibuprofen, High IBU = 30 μg/ml ibuprofen (HIBU). (A) Mammary fibroblast morphology when cultured on plastic (left panel) or within floating collagen pads (right panel). Dashed lines show the outline of the cells. (B) α-Smooth muscle actin (αSMA) gene expression in primary mammary fibroblasts cultured on plastic, within floating collagen pads, or from freshly sorted mammary PDGFRα+ fibroblasts, n = 6–10 per condition. (C) Morphologic evidence of TGF-β1–induced fibroblast activation in the floating collagen pad culture model. (D) Increased Col1a1 and Cox2 gene expression in fibroblasts treated with TGF-β1, n = 4–7 per condition. (E) The ability of TGF-β1–treated fibroblasts to contract collagen pads (top) is suppressed by ibuprofen (bottom) and (F) data quantification, n = 5 per condition. (G) Fibroblast morphology with TGF-β1 treatment in the presence or absence of ibuprofen. (H) Col1a1 and Cox2 gene expression in fibroblasts with TGF-β1 treatment in the presence or absence of ibuprofen, n = 5 per condition. Scale bars: 100 μm (A, C, and G) and 1 cm (E). All gene expression data are normalized to Actb and then normalized to the control groups in each experiment. TGF-β1 and ibuprofen combination treatment studies were repeated 5 times. *P < 0.05, **P < 0.01, ***P < 0.001, #P < 0.0001 by 1-way ANOVA with Tukey correction. For data normalized to control, statistics were performed using matched 1-way ANOVA with Tukey correction on the raw data that are not normalized to control. Data represent mean ± SEM. NS, not significant.